Fiber optic darkfield ring light

ABSTRACT

A fiber optic darkfield ring light with many angled fiber optic light lines with direct illumination in a very small package. The fiber optic darkfield ring light includes a base with multiple light heads and multiple light covers attached thereto, a main cover, an optional cord grip, and an optional hood. It incorporates multiple fiber optic line arrays positioned at low angle and used in conjunction with a strobe light source.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional PatentApplication No. 60/486,502, filed on Jul. 11, 2003, and entitled FIBEROPTIC DARKFIELD RING LIGHT.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to dark field illumination as is widelyused in machine vision to detect features higher or lower than regularsurfaces.

2. Background Information

Over the past several decades, the semiconductor has exponentially grownin use and popularity. The semiconductor has in effect revolutionizedsociety by introducing computers, electronic advances, and generallyrevolutionizing many previously difficult, expensive and/or timeconsuming mechanical processes into simplistic and quick electronicprocesses. This boom in semiconductors has been fueled by an insatiabledesire by business and individuals for computers and electronics, andmore particularly, faster, more advanced computers and electronicswhether it be on an assembly line, on test equipment in a lab, on thepersonal computer at one's desk, or in the home electronics and toys.

The manufacturers of semiconductors have made vast improvements in endproduct quality, speed and performance as well as in manufacturingprocess quality, speed and performance. However, there continues to bedemand for faster, more reliable and higher performing semiconductors.

Processors who are building semiconductors and like microelectronicsmust be able to provide ample illumination for the machine visionprocess. Users of inspection equipment continue to demand smaller, moreintense, more robust illumination.

In the past, it was typical to use halogen, laser or other illuminationmethods rather than fiber optic. Where fiber optic has been tried, thesetup has typically involved using a metal ring with a polished surfaceattached to standard fiber optic ring light to achieve some dark fieldillumination.

SUMMARY

An illuminator including a base with multiple light heads attachedthereto, and fiber optics provided in each of the multiple heads.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiment of the invention, illustrative of the best mode inwhich applicant has contemplated applying the principles, are set forthin the following description and are shown in the drawings and areparticularly and distinctly pointed out and set forth in the appendedclaims. Similar numerals refer to similar parts throughout the drawings.

FIG. 1 is a diagram illustrating an automated defect inspection systemaccording to one embodiment of the present invention.

FIG. 2 is a diagram illustrating a perspective view of one embodiment ofa fiber optic darkfield ring light in a partially assembled state.

FIG. 3 is a diagram illustrating a top view of the fiber optic darkfieldring light shown in FIG. 2 in an assembled state according to oneembodiment of the present invention.

FIG. 4 is a diagram illustrating a cross-sectional view of the fiberoptic darkfield ring light along section lines 4-4 in FIG. 3 accordingto one embodiment of the present invention.

FIG. 5 is a diagram illustrating a top view of a light head according toone embodiment of the present invention.

FIG. 6 is a diagram illustrating a front view of the light head shown inFIG. 5 according to one embodiment of the present invention.

DETAILED DESCRIPTION

FIG. 1 is a diagram illustrating an automated defect inspection system10 according to one embodiment of the present invention. System 10 isused in one environment to find defects on die on patterned wafers, butis intended for this and other uses including for inspecting wholewafers, sawn wafers, broken wafers, wafers of any kind on film frames,die in gel paks, die in waffle paks, MCMs, JEDEC trays, Auer boats, andother wafer and die package configurations (although hereinafter all ofthese uses shall be referred to generally as inspection of wafers orsubstrates).

System 10 includes a wafer test plate 12, means for providing a wafer tothe test plate referred to as 14, a wafer alignment device 16 foraligning each and every wafer at the same x, y, and θ location or x, y,z, and θ location, a focusing mechanism 18, a camera 20 or other visualinspection device for visual inputting of good die during training andfor visual inspection of other unknown quality die during inspection, aparameter input device 22 for inputting parameters and other constraintsor information such as sensitivity parameters, geometries, die size, dieshape, die pitch, number of rows, number of columns, etc., a display 24for displaying the view being seen by the camera presently or at anypreviously saved period, a computer system 26 or other computer-likedevice having processing and memory capabilities for saving the inputtedgood die, developing a model therefrom, and comparing or analyzing otherdie in comparison to the model, a frame 30, a hood 32, a control panel34, a system parameters display 36, objective 38, and a fiber opticdarkfield ring light 40.

The means for providing a wafer to the test plate referred to as 14 maybe either manual in that the user moves the wafer from a cassette ormagazine to the test plate 12, or automatic as is shown in theembodiment of FIG. 1. In the automatic environment, the wafer providingmeans 14 includes a robotic arm that pivots from a first position wherea wafer is initially grasped from a magazine or cassette to a secondposition where the wafer is positioned on the wafer test plate 12 forinspection. After inspection, the robotic arm pivots the wafer from thesecond position at the test plate 12 back to the first position wherethe wafer is placed back in or on the magazine or cassette.

In one form of the invention, system 10 is trained as to what a “gooddie” comprises by aligning via device 16 and viewing via camera 20 aplurality of known good die and forming a model within computer system26 to define what an ideal die should look like based upon the commoncharacteristics viewed. In one embodiment, after being trained, system10 is used to inspect die of unknown quality. During inspectionaccording to one embodiment, system 10 collects an image of a waferusing the camera 20 by moving the plate 12 to align the camera with afirst die or other portion thereof, viewing and recording that die orportion thereof by opening the shutter and allowing the camera to viewand record the image, moving the plate 12 to align the camera with asecond die or portion thereof, viewing and recording the second die orportion thereof, and repeating these steps until all of the die orportions thereof on the wafer that are desired to be viewed have beenviewed and recorded. In one embodiment, system 10 determines wheredefects are located on a given die being viewed based upon the “gooddie” model.

In another embodiment, rather than using a stop and go procedure tocapture images of die on the wafer, system 10 collects an image of thewafer using the camera 20 by continuously moving the plate 12 so as toscan over all of the die on the wafer, whereby the wafer is illuminatedby a strobe light at a sequence correlating to the speed of the movingplate so that each die is strobed at the precise time it is under thecamera 20. This allows for the continuous collecting of images withoutnecessitating the stop and go procedure of aligning the camera with afirst die, viewing and recording that die, moving the plate 12 to alignthe camera with a second die, viewing and recording this second die, andrepeating these steps until all of the die on the wafer have been viewedand recorded, etc.

In one embodiment, fiber optic darkfield ring light 40 is mountedbetween two millimeters and five millimeters above test plate 12.Substrates to be inspected are placed through an inspection region 94(shown in FIG. 2) of ring light 40, and rest on test plate 12. Ringlight 40 provides darkfield illumination to substrates as described infurther detail below with reference to FIGS. 2-6.

The fiber optic darkfield ring light 40 of the present invention isshown in FIG. 2, and in general consists of many angled fiber opticlight lines with direct illumination in a very small package that is atleast 1/5 of the thickness of other known ring light systems. Ring light40 according to one embodiment provides very intense dark fieldillumination and is sized so as to be capable of use with multipleobjectives in an inspection system. This unique design enables newinspection capabilities including nodules, craters, particles and othersurface defects. It also enables inspection of very dark wafers inbright field due to wafer micro-roughness.

In more detail, the fiber optic darkfield ring light 40 as shown in FIG.2 includes a base 60 with multiple light heads 80 attached thereto (withone removed and pointed out as 80) and multiple light covers 74 attachedthereto (with one removed and pointed out as 74), a main cover 42, anoptional cord grip 52, and an optional hood 48. The fiber opticdarkfield ring light 40 in the embodiment shown has eight (8) fiberoptic line arrays 90 (where each line array 90 includes a light head 80,a light cover 74 and fiber optics that are shown in FIGS. 3 and 6)positioned at a low angle (15 degrees for the embodiment shown). In oneembodiment, the system 40 is used in conjunction with a strobe lightsource.

The base 60 provides a mounting surface for the multiple fiber opticline arrays 90. In the embodiment shown, the base 60 provides a mountingsurface for eight (8) fiber optic line arrays 90. The base 60 in moredetail is a block with a top base surface 105 and a recessed area 64therein having a first surface portion 70A on which the light heads 80are mounted. The recessed area 64 is generally cylindrical in shape, andis defined by a wall 66 and a bottom recess surface 68. The bottomrecess surface 68 includes the first surface portion 70A on which thelight heads 80 are mounted, and a second surface portion 70B extendingoutward from and surrounding the first surface portion 70A. In theillustrated embodiment, surface portions 70A and 70B are ring-shaped. Inthe embodiment shown, the mounted heads 80 have an inward taper and arepositioned in a generally circular manner around an inspection region94. A fiber optic routing channel 72 is defined behind the light heads80 and appears as an annual ring area. The surface 70A in the recessedarea 64 on which the light heads 80 are mounted is designed in oneembodiment in a polygonal fashion, in the embodiment shown an octagonalpattern with eight notches 92 extending upward from surface 70A foreight (8) fiber optic line arrays 90, to simulate a true circular ring.A cutout notch 62 from the routing channel 72 is notched out of the base60, thereby providing a lateral access into the recessed area 64.

Each light head 80 includes a channel 82 formed therein that providesroom for an individual set or group of fiber optic lines for each fiberoptic line array 90 (as shown in FIG. 6). Each light cover 74 provides acover for an individual set or group of fiber optic lines for each fiberoptic line array 90. The main cover 42 or multi-head cover protects thefiber optics once assembled by covering the routing channel 72.

The cord grip 52 provides a transition for all fiber optics from eight(8) fiber optic line arrays 90 to one (1) fiber optic input bundle thatis placed within the cord grip 52 positioned at the cut-out notch 62(and attachable there). The fiber optic input bundle is positionedwithin a circular hole 56 in cord grip 52. The hood 48 providesprotection for fiber optics in the transition into the unit 40 and alsomay assist in securing the fiber optics in place.

Assembly of the fiber optic darkfield ring light 40 occurs as follows inone embodiment: Assemble multiple fiber optic line arrays 90 where eachline array 90 includes a light head 80, a light cover 74 and fiberoptics (shown in FIGS. 3 and 6). Route all fiber optics through hole 56of the cord grip 52. Position and secure the main cover 42 and positionand secure the hood 48.

FIG. 3 is a diagram illustrating a top view of the fiber optic darkfieldring light 40 shown in FIG. 2 in an assembled state according to oneembodiment of the present invention. As shown in FIG. 3, a first end ofa fiber optic input bundle 102 is positioned within cord grip 52 of ringlight 40. In one embodiment, the fiber optic bundle 102 includeshundreds of individual fiber optic lines. In one embodiment, the fiberoptic lines in bundle 102 are separated in the routing channel 72 (FIG.2) into eight groups or sets 104 of fiber optic lines. Only five sets104 of fiber optic lines are shown in FIG. 3 to simplify theillustration. In one embodiment, each set 104 of fiber optic linesincludes a plurality of fiber optic lines. Each set 104 of fiber opticlines is routed through the routing channel 72 (FIG. 2) to one of theline arrays 90. The sets 104 of fiber optic lines are represented inFIG. 3 by hidden lines, since the fiber optic lines are covered by maincover 42.

As shown in FIG. 3, fiber optic darkfield ring light 40 has a length, L,and a width, W. In one embodiment, L and W are each 3.75 inches. Thelength and width of ring light 40 depend upon the size of objects to beilluminated. In other embodiments, ring light has a length and/or widththat are greater or less than 3.75 inches.

In use, the ring light system 40 uses fiber optics 104 to deliver lightfrom a light source 103 (such as a strobing light source) to the area tobe inspected in the inspection region 94, which is at the center of thesubstantially circular arrangement of line arrays 90. In one embodiment,light source 103 provides light that is directed by fiber optic inputbundle 102 to ring light 40. The light is then directed by each set 104of fiber optic lines to corresponding ones of the line arrays 90, whichdirect the light to inspection region 94. In one form of the invention,light source 103 strobes to provide short flashes of light that arecorrelated with a velocity or position of a substrate being inspected.The multiple (in the embodiment shown eight) fiber optic line arrays 90deliver intense light in a very small profile, and at a low angle (suchas 15 degrees) from the fiber optic line arrays 90 to the inspectionsurface. This angle is determined by the angle of the mounting surfaceportion 70A (FIG. 2) on the base 60, as will be described in furtherdetail below with reference to FIG. 4.

FIG. 4 is a diagram illustrating a cross-sectional view of the fiberoptic darkfield ring light 40 along section lines 4-4 in FIG. 3according to one embodiment of the present invention. Surface 70A ofbase 60 is at an angle, θ, with respect to a bottom base surface 106 ofring light 40. The bottom base surface 106 of ring light 40 defines ahorizontal plane (perpendicular to the paper in FIG. 4) that is parallelto the surface to be inspected). Since line arrays 90 are mounted on theangled surface 70A, line arrays 90 are also at an angle, θ, with respectto the bottom base surface 106 of ring light 40, and with respect to thesurface to be inspected. Thus, line arrays 90 deliver light at an angle,θ, to an object placed in the inspection region 94. In one embodiment,the angle, θ, is 15 degrees. In other embodiments, the angle, θ, is inthe range of 5 to 25 degrees. In the illustrated embodiment, surfaceportion 70B is parallel to the bottom base surface 106 and the surfaceto be inspected.

As shown in FIG. 4, base 60 has a height or thickness, T. In oneembodiment, T is less than about 0.5 inches. In one form of theinvention, T is equal to 0.35 inches. With a thickness of only 0.35inches in one embodiment, ring light 40 is sized so as to be capable ofuse with multiple objectives in an inspection system. The objectives ininspection systems are typically mounted on a rotating turret. The lowprofile of ring light 40 allows the different objectives to be rotatedinto position without the interference that would be caused by a higherprofile lighting system.

FIG. 5 is a diagram illustrating a top view of one of the light heads 80of ring light 40 according to one embodiment of the present invention.As shown in FIG. 5, light head 80 is tapered such that the width of thelight head 80 becomes narrower moving from the back of the light head 80(at the top of FIG. 5) to the front of the light head 80 (at the bottomof FIG. 5). Channel 82 is formed in light head 80. A set 104 of fiberoptic lines from fiber optic bundle 102 (FIG. 3) is routed through theback of the light head 80 to the front of the light head 80, and directslight out of the front of the light head 80.

FIG. 6 is a diagram illustrating a front view of the light head 80 shownin FIG. 5 according to one embodiment of the present invention. As shownin FIG. 6, a set 104 of fiber optic lines are positioned in the channel82 of the light head 80. In one embodiment, the fiber optic lines ineach light head 80 are configured in a light line configuration, so thateach line array 90 outputs a horizontal line of light. In the light lineconfiguration according to one form of the invention, the set 104 offiber optic lines for each light head 80 is in the form of a fiber opticbundle with a relatively flat, rectangular shape, such as shown in FIG.6. In effect, each fiber optic line array 90 converts a point source toa line of light, and this design provides for multiple, such as 8-linesat a low angle (15 degrees for the illustrated embodiment) to create avery low profile, intense dark field ring light 40.

The unique fiber optic darkfield ring light system 40 according to oneembodiment provides intense dark field illumination to highlightfeatures that are higher or lower in height than a regular surface.Examples of such features are nodule and crater defects on the bump topof gold bumped wafers, particles and scratches on surface, etc. Thesystem 40 can be used alone or with other bright field illumination. Thesystem 40 is of much smaller profile compared to off-the-shelf productsto provide maximum flexibility with current optics.

In sum, the system 40 is a fiber optic darkfield ring light forillumination. One application is darkfield illumination for use indefect inspection on semiconductors and microelectronics where itilluminates to assist in inspection for defects. One type of defect thatit is useful in finding is nodules and craters. It is also very usefulfor defect detection on gold bump wafers and others wafers with flatbump top. This system is also useful for assisting in defect detectionfor surface defect detection such as on any relatively flat surface.Overall, it provides for a very low profile, intense dark field ringlight 40 for general machine vision and the microscopy industry.

Accordingly, the invention as described above and understood by one ofskill in the art is simplified, provides an effective, safe,inexpensive, and efficient device, system and process which achieves allthe enumerated objectives, provides for eliminating difficultiesencountered with prior devices, systems and processes, and solvesproblems and obtains new results in the art.

In the foregoing description, certain terms have been used for brevity,clearness and understanding; but no unnecessary limitations are to beimplied therefrom beyond the requirement of the prior art, because suchterms are used for descriptive purposes and are intended to be broadlyconstrued.

Moreover, the invention's description and illustration is by way ofexample, and the invention's scope is not limited to the exact detailsshown or described.

Having now described the features, discoveries and principles of theinvention, the manner in which it is constructed and used, thecharacteristics of the construction, and the advantageous, new anduseful results obtained; the new and useful structures, devices,elements, arrangements, parts and combinations, are set forth in theappended claims.

1. A darkfield illuminator, comprising: a base; a plurality of lightheads attached to the base; a plurality of fiber optic lines; andwherein each of the light heads is configured to hold a set of the fiberoptic lines and provide darkfield illumination.
 2. The darkfieldilluminator of claim 1, wherein the base includes a recess formedtherein.
 3. The darkfield illuminator of claim 2, wherein the recess issubstantially cylindrical in shape.
 4. The darkfield illuminator ofclaim 2, wherein the recess is defined by a bottom recess surface and awall substantially surrounding the bottom recess surface.
 5. Thedarkfield illuminator of claim 4, wherein the bottom recess surfaceincludes a first surface portion that is angled with respect to asurface to be illuminated.
 6. The darkfield illuminator of claim 5,wherein the light heads are attached to the first surface portion in asubstantially circular arrangement, and are configured to provide lightfrom the fiber optic lines toward a center of the substantially circulararrangement. 7.-12. (canceled)
 13. The darkfield illuminator of claim 1,wherein the plurality of light heads includes at least eight lightheads.
 14. The darkfield illuminator of claim 1, wherein the set offiber optic lines held by each of the light heads includes a pluralityof fiber optic lines that are arranged in a light line configuration,such that the plurality of light heads provides a correspondingplurality of lines of light.
 15. The darkfield illuminator of claim 1,wherein the base is less than about one-half inch in height.
 16. Thedarkfield illuminator of claim 1, wherein the base is about 0.35 inchesin height.
 17. An automated inspection system for inspecting asubstrate, comprising: a darkfield illumination device for illuminatingthe substrate with darkfield illumination, the darkfield illuminationdevice including a base having a recess formed therein, the baseincluding a bottom surface at a bottom of the recess, the bottom surfaceincluding a first surface portion that is angled with respect to asurface to be illuminated, the darkfield illumination device including aplurality of light heads attached to the first surface portion in asubstantially circular arrangement, the light heads each including aplurality of fiber optic lines for providing light toward a center ofthe substantially circular arrangement at an angle corresponding to theangle of the first surface portion; a substrate provider for providingthe substrate within the substantially circular arrangement of lightheads; a visual inspection device for capturing images of the substrateprovided by the substrate provider; and a controller for identifyingdefects in the substrate based on the captured images.
 18. The automatedinspection system of claim 17, wherein the recess is substantiallycylindrical in shape. 19.-25. (canceled)
 26. The automated inspectionsystem of claim 17, wherein the plurality of light heads includes atleast eight light heads.
 27. The automated inspection system of claim17, wherein the plurality of fiber optic lines in each of the lightheads are arranged in a light line configuration, such that theplurality of light heads provide a corresponding plurality of lines oflight.
 28. The automated inspection system of claim 17, wherein thedarkfield illumination device is configured to strobe based on avelocity of the substrate.
 29. A method of providing darkfieldillumination, the method comprising: providing a base having a recessformed therein, the recess defined by a bottom surface and a wallsubstantially surrounding the bottom surface, the bottom surfaceincluding a first surface portion that is angled with respect to asurface to be illuminated; attaching a plurality of light heads to thefirst surface portion in a substantially circular arrangement, the lightheads each including a plurality of fiber optic lines; and transmittinglight through the fiber optic lines of each light head, therebyproviding darkfield light toward a center of the substantially circulararrangement at an angle corresponding to the angle of the first surfaceportion.
 30. An illuminator comprising: a base with multiple light headsattached thereto; and fiber optics provided in each of the multipleheads for providing darkfield illumination.